I wouldn't say he was a complete unknown as he was featured last year as well, but still not a high ranked player. What is more incredible perhaps is that this is the fourth year is a row that Nadal has gone out to a player ranked outside the top 50.

He used to sometimes make the odd half hearted attempt to return a ball or two, but never for a full game that I remember and he certainly at least made an attempt at a return. Kyrgios just let three returnable balls go past him.

I've seen a few players have a game where they have a rest and just return into the net each point or barely make an effort, but not even going for the ball is poor. Don't think there's anything in the rules to say they can't, though, unless it's counted as unsporting behaviour or similar.

E. BEST EFFORTSA player shall use his best efforts to win a match when competing in a Grand Slam Tournament. Violation of this section shall subject a player to a fine up to $20,000 for each violation. For purposes of this Rule, the Referee and/or the Chair Umpire shall have the authority to penalise a player in accordance with the Point Penalty Schedule.